Registry offices in Shanghai have begun warning couples on the brink of break-up that property booms are only temporary, but a divorce can last forever.

The warning, which draws an unorthodox link between marital harmony and the prevailing health of China’s property market, is aimed at a very particular type of couple: the sort whose impending divorce will be a complete sham.

Recent changes to the tax law, in particular a new capital gains levy on sales of second homes, have produced an immediate and destructive effect on the Chinese institution of marriage. Divorce rates in big, “tier-1” cities with